1. Field of the Invention
This invention relates to an antenna for the broadcast of electromagnetic wave energy and, more particularly, to class of antennas known as slotted antennas.
2. Description of the Prior Art
Slotted antennas generally have a conductive mast that has a plurality of layers with one or more slots in each layer that are positioned along the axial direction of the mast. Slotted antennas have been used to radiate horizontally polarized waves for television applications. To impart elliptical or circular polarization, separate dipoles have been placed in juxtaposition to the slots. The dipoles are operable to provide a vertical component of radiation to the horizontal component provided by the slots. Examples of slotted antennas with elliptical polarization are disclosed in U.S. Pat. Nos. 4,129,871 and 4,899,165.
Some slotted antennas require a standing wave design. A standing wave design requires the admittance of each layer to add in parallel such that the resulting input admittance achieves a desired bandwidth at the antenna input. In order to achieve the best overall bandwidth at the antenna input, it is desirable to add up admittances of the layers along the real axis of the Smith chart. The slots of current standing wave antennas tend to have a high enough susceptance that it is difficult to achieve the best overall bandwidth at the antenna input.
An object of the present invention is to provide an antenna with reduced slot susceptance and improve antenna bandwidth.